1. Field of the Invention
The present invention relates to a digital color copying machine, and more particularly, to a digital copying machine capable of performing a mosaic monitor mode for making a color adjustment.
2. Description of the Related Art
A conventional digital color copying machine comprises a reading section for reading an image of a document by using a color image sensor and converting the image of the document into image data for printing, and a printer section for printing an image of the document on a copying paper according to the image data. In the case that plural color images are to be superimposed on a copying paper, the document is read repeatedly by the reading section, and each color image is printed on the same copying paper by the printer section in the order of respective colors predetermined.
The reading section comprises a masking process for generating a color-corrected signal corresponding to printing characteristics of the printer section. Generally speaking, it is difficult for the masking process circuit to minimize the color difference between the real document and the copy thereof with respect to all the colors contained therein. Therefore, in the case where a copy is further copied as a document, the color tone of the secondary copy may be considerably different from that of the original document. However, in a limited color tone range, if a better color balance adjustment is performed, the variation of the color tone can be minimized.
Conventionally, the color balance adjustment is performed in a manner of so-called cut and try. In this case, the scanning operation of the document is repeated a number of times, the number of times being a product of the number of times the color balance operation is needed to obtain a desired color copy and the number of the printing colors. Therefore, the color balance operation is time consuming and laborious.
The inventors of the present invention have proposed a color adjustment selecting method (referred to as a mosaic monitor method hereinafter) for decreasing time and cost required for the color correction in the U.S. patent application Ser. No. 321,405. In this mosaic method, an area of a document (referred to as a specific area hereinafter) including a partial image, for example a face of a person, is set by a specific area setting means. Then, image data from each specific area is stored in an image memory means. Next, a color adjustment is made for the image data read from the image memory means with predetermined various color correction levels, and the various sets of color corrected image data are printed at different positions on the same copying paper in a mosaic-like pattern. Thereafter, the operator selects an image having a color balance nearest to that of the document or an image having a color balance desirable for the operator from plural images of the specific area (referred to as a mosaic monitor image hereinafter) which have been reproduced with different color balances, respectively. Thereafter, a copy of the whole area of the document is produced based on the color correction level of the mosaic monitor image selected. Thus, a copy of the document having a desirable color balance can be obtained easily.
However, in the case that there is no image for which a desirable color adjustment is made in the mosaic monitor mode, the operator has to repeat the mosaic monitor operation until an image having a desirable color balance is obtained. In this case, the document is scanned many times repeatedly. In particular, if the operator wishes to reproduce a skin color of a portrait faithfully, the color balance adjustment has to be performed repeatedly until a desirable skin color of the portrait is realized. Further, in such a case that the operator wishes to vary the standard color correction level, it is desirable to print mosaic monitor images after the standard color correction level has been changed.
Furthermore, in a copying machine wherein the density level is adjustable according to the density of the document image, the density level may be different from a standard level upon entering the mosaic monitor mode. In such a case, the mosaic monitor images are printed on a copying paper with the set density level.
Since the density level is closely related to the color balance of individual mosaic image, the color balance selected at a density level different from the standard density level may give a different color balance under the standard density level.